Refining of cathode copper



Patented Jan. 3, 1939 PATENT OFFICE REFINING OF CATHODE COPPER Lon Bercovici, Brussels, Belgium, assignor to Socit Gnrale Mctallurglque de Hoboken,

Hoboken, near Antwerp, Belgium No Drawing. Application February 5, 1938, Serial No. 188,925

4Glaims.

This invention relates to the refining of cathode copper substantially free from oxygen and containing appreciable quantities of hydrogen.

When casting whilst protecting from the ac- 5 tion of the air cathode copper which has. not been degasified or has not been sumciently degasifled, it has been ascertained that at the point of solidification, that is 1084 0., part of the hydrogen contained by the molten copper escapes during the solidification process. Another part of the hydrogen is retained by the semi-solid copper, thus producing a porosity which is characteristic of the presence of hydrogen, while a third portion of H, which must be lower than 2.12 cc. per

100 grams of copper may remain in solution in the copper.

The solubility of hydrogen in copper varies with the temperature of the copper, the following table giving the amounts of hydrogen which remain in equilibrium inside the copper at various temperatures:

It'has now been ascertained that if for example cathode copper is heated at say 981 C., whilst protecting it from the air, for a sufllcient time to allow the escape of hydrogen, and if the copper thus pre-treated, still contains more than 1.4? cc. H2 but less than 2.12 cc. Hz and is melted and cast, whilst protecting it from the action of the 40 air, the H2 remaining in the copper has no prejudical effect on the quality of the copper. If however, at the moment of casting the amount of H contained by the copper is near to 2.12 cc. per 100 grams of copper, the molten copper should be cast and chilled rapidly, e. g., into molds provided with intensive water cooling, allowing a rapid chilling of the metal. In this way the residual H can be held in solution.

The cathode copper is therefore heated, whilst protecting it from air and any other impurities such as combustion gases and whilst carefully avoiding its melting, until the amount of hydrogen which is left inside the copper is equal to, or smaller than that corresponding to the equilibrium between hydrogen and copper at the melting point of the still solid copper; the cathode copper is thereupon melted inside the same furnace and is cast immediately, whilst protecting it from the air and other impurities.

In all cases, whatever the temperature of heating may be, the amount of hydrogen left in the metal should be smaller than 2.12 cc. H2 per gr. of copper.

Also in all cases the temperature of heating should be below the melting point of the copper. 10

Preferably, the cathodes are placed in the furnace upon a charcoal bed and the heating is effected at temperatures between 900 and 1000 C. Provision should be made to allow the escape from the furnace of the gases which escape from the 15 metal. These gases burn 2in contact with the atmospheric air and the length of the flame allows of watching the progress of the elimination of gas.

In practice, as soon as the cathodes have been 20 charged, the charging door is closed, whilst leaving an opening sufficient to allow the gases from the furnace to escape to the outside.

The heating is commenced and as soon as the cathodes have reached a certain temperature, 25 the escape of the dissolved or occluded hydrogen commences. This moment can be recognized by the fact that the flame which escapes through the charging door becomes longer. The length of this flame allows of following the elimination 30 of the gas, from outside the furnace.

Towards the end of the operation, the flame becomes progressively shorter until it reaches a length which does not vary any more. At that moment, the elimination of hydrogen from the 35 cathodes, has ceased, and the residual gas retained by the copper is in equilibrium with the latter, at the available temperature.

The indication given by the flame is very clear and allows of following the degasifying process, 40 without the possibility of a mistake being made.

The furnace preferably used is a rotary or tilting electric radiating furnace of some known typ for instance an electric radiating furnace in which the heating resistance or resistances is or 45 are arranged substantially along the axis of rotation of the furnace without coming into contact with the copper.

After the required amount of hydrogen has been allowed to escape, the charge is melted and as 60 soon as it has been brought to the molten state, it is cast into molds, enabling a rapid cooling, whilst avoiding its contact with atmospheric air, for instance by protecting the jet of metal by means of a surrounding structure, and/or by 55 sweeping the inside of the mold with suitable gases.

I claim:

1. A process for the treatment of cathode cop- D6! which is substantially free from oxygen and which contains appreciable quantities of hydrogen, comprising the steps of heating'the cathode copper inside a furnace at a temperature sufllciently below the melting point to avoid even the partial melting, of the copper whilst protecting it from the atmospheric air and from all impurities, such as combustion gases, and allowing the hydrogen to escape, continuing the heating without melting until the percentage of hydrogen left in the copper is equal to, or lower than the amount corresponding to the equilibrium between copper and hydrogen at the melting point of the still solid copper and in all cases below 2.12 cc. per grams of cathode copper, melting afterwards the charge inside the same furnace and casting it after melting, whilst protecting it from the atmospheric air.

2. A process for the treatment of cathode copper which is substantially free from oxygen and which contains appreciable quantities of hydrogen, comprising the steps of placing the cathode copper upon a bed of charcoal inside an electric radiating furnace, heating the cathode copper at a temperature suiliciently below the melting point to avoid even the partial melting *of the copper, whilst protecting it from the atmospheric air and from all impurities, such as combustion gases, and allowing the hydrogen to escape, continuing the heating without melting until the percentage of hydrogen left in the copper is equal to, or lower than the amount corresponding to the equilibperature of heating and in all cases below 2.12 cc.

'per 100 grams of cathode copper, melting afterwards the charge inside the same furnace and casting it after melting, whilst protecting it from the atmospheric air.

3. A process for the treatment of cathode copper which is substantially free from oxygen and which contains appreciable quantities of hydrogen, comprising the steps of heating the cathode copper inside a radiating electric furnace at between 900 and 1000 C., whilst protecting it from the atmospheric air and from all impurities, such as combustion gases, and allowing the hydrogen to escape, until the percentage of hydrogen left in the cathode copper is lower than 2.12 cc. Hz per 100 grams of cathode copper, melting afterwards the charge inside the same furnace and casting it after melting, whilst protecting it from the atmospheric air.

, 4. A process for the treatment of cathode copper which is substantially free from oxygen and which contains appreciable quantities of hydrogen, comprising the steps of heating the cathode copper inside a radiating electric furnace at between 900 and 1000 C., whilst protecting it from the atmospheric air and from all impurities, such as combustion gases, and allowing the hydrogen to escape, until the percentage of hydrogen left in the cathode copper is equal or lower than 2.12 cc. of H2 per 100 grams of cathode copper, melting afterwards the charge inside the same furnace and casting it after melting, whilst protecting it from the atmospheric air, so as to be rapidly chilled as set forth.

. LEON BErwovIcI. 

